The present invention relates to a motor control apparatus and a motor system. More particularly, the present invention relates to a motor control apparatus and a motor system that can drive a permanent magnet synchronous motor without using a sensor for detecting a rotor position.
Among position sensor-less control technologies for controlling a permanent magnet synchronous motor without using a sensor for detecting a rotor position, a controlling method of a motor by measuring a terminal voltage of the motor and controlling the motor on the basis of the terminal voltage has been primarily used for driving apparatuses of motors having relatively low voltages. This method will be hereinafter called a “terminal voltage detection system”.
As one of the terminal voltage detection systems, JP-A-2007-151351 discloses a technology that turns off all switching devices of a three-phase inverter at an arbitrary timing, measures the terminal voltage of the motor under a state where power is not fed to all the phases and estimates a rotor position.
This technology according to JP-A-2007-151351 can improve load follow-up performance in low speed revolution because it can shorten an observation cycle of the terminal voltage when the rotor position is estimated from the terminal voltage of the motor.